Change type of ReplaceChars() parameter.

Currently base::ReplaceChars() accepts std::string for the 3rd
parameter, and immediately converts it to base::StringPiece.

To avoid string copies on the caller side, it should accept
base::StringPiece instead.

This change became possible after r504430.

BUG=760330
TEST=base_unittests --gtest_filter=StringUtilTest.ReplaceChars

Change-Id: I9a3a4cc02cfbfb8c8a258dc077612dd5146b9592
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1930799
Auto-Submit: Andrei Polushin <anpol@yandex-team.ru>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719410}

base/strings/string_util.cc

@@ -237,17 +237,16 @@ bool ReplaceCharsT(const StringType& input,
 
 bool ReplaceChars(const string16& input,
                   StringPiece16 replace_chars,
-                  const string16& replace_with,
+                  StringPiece16 replace_with,
                   string16* output) {
-  return ReplaceCharsT(input, replace_chars, StringPiece16(replace_with),
-                       output);
+  return ReplaceCharsT(input, replace_chars, replace_with, output);
 }
 
 bool ReplaceChars(const std::string& input,
                   StringPiece replace_chars,
-                  const std::string& replace_with,
+                  StringPiece replace_with,
                   std::string* output) {
-  return ReplaceCharsT(input, replace_chars, StringPiece(replace_with), output);
+  return ReplaceCharsT(input, replace_chars, replace_with, output);
 }
 
 bool RemoveChars(const string16& input,

base/strings/string_util.h

@@ -184,11 +184,11 @@ BASE_EXPORT bool RemoveChars(const std::string& input,
 // NOTE: Safe to use the same variable for both |input| and |output|.
 BASE_EXPORT bool ReplaceChars(const string16& input,
                               StringPiece16 replace_chars,
-                              const string16& replace_with,
+                              StringPiece16 replace_with,
                               string16* output);
 BASE_EXPORT bool ReplaceChars(const std::string& input,
                               StringPiece replace_chars,
-                              const std::string& replace_with,
+                              StringPiece replace_with,
                               std::string* output);
 
 enum TrimPositions {